Re: [PATCH] s390/pai: Simplify pai_init() and always return -ENODEV on failure

[Heiko Carstens <hca@linux.ibm.com>]

On Mon, Sep 21, 2026 at 01:40:21PM +0200, Thomas Richter wrote:
> On 9/14/26 14:14, Heiko Carstens wrote:
> > On Thu, Sep 03, 2026 at 10:15:57AM +0200, Thomas Richter wrote:
> >> Code simplification and remove variable state.
> >> Return -ENODEV in all failures to indicate the PAI PMUs are not
> >> available.
> > 
> > Why do you want to hide different error / return codes? That makes
> > debugging in case of an error more difficult.
> 
> Well, hiding was not the intent.
> 
> The kernel common code does a lot of checks at event creation,
> then calls the PMU event_init() call back to install the event.
> When this fails the return code is checked and further action
> depends on this return code. See
> 
>   perf_init_event()
>   +--> perf_try_event_init()
>        +--> PMU->event_init()
> 
> See include/linux/perf_event.h for return code meanings.
> 
> When we return the value from cpuhp_setup_state(), it must no be
> -ENOENT and some other values. Because those are used for postprocessing.
> 
> Thats why I always return -ENODEV, meaning event is valid for PMU, but
> PMU not operational. I thouhgt this might fit best.

But what does have pai_init() to do with anything of the above?
pai_init() is called via init_call() mechanism.